A drop hitting a solid surface can deposit, bounce, or splash. Splashing arises from the breakup of a fine liquid sheet that is ejected radially along the substrate. Bouncing and deposition depend crucially on the wetting properties of the substrate. In this review, we focus on recent experimental and theoretical studies, which aim at unraveling the underlying physics, characterized by the delicate interplay of not only liquid inertia, viscosity, and surface tension, but also the surrounding gas. The gas cushions the initial contact; it is entrapped in a central microbubble on the substrate; and it promotes the so-called corona splash, by lifting the lamella away from the solid. Particular attention is paid to the influence of surface roughness, natural or engineered to enhance repellency, relevant in many applications.

https://hal.archives-ouvertes.fr/hal-01398138/document

Drop Impact on a Solid Surface

This paper gives a comprehensive review about the most recent progress in synthesis, characterization, fundamental understanding, and the performance of graphene and graphene oxide sponges. Practical applications are considered including use in composite materials, as the electrode materials for electrochemical sensors, as absorbers for both gases and liquids, and as electrode materials for devices involved in electrochemical energy storage and conversion. Several advantages of both graphene and graphene oxide sponges such as three dimensional graphene networks, high surface area, high electro/thermo conductivities, high chemical/electrochemical stability, high flexibility and elasticity, and extremely high surface hydrophobicity are emphasized. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.

A review of graphene and graphene oxide sponge: material synthesis and applications to energy and the environment

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Superwettability is a special case of the wetting phenomenon among liquids, gases, and solids. The superhydrophobic/superhydrophilic effect discovered initially has undergone a century of development based on materials science and biomimetics. With the rapid development of research on anti-wetting materials, superoleophobic/superoleophilic surfaces have been fabricated to repel organic liquids besides water. Further studies of underwater superoleophobic/superoleophilic/superaerophobic/superaerophilic materials provide an alternative way to fabricate anti-wetting surfaces rather than lowering the surface energy. Owing to a series of efforts on the studying of extreme wettabilities, a mature superwettability system gradually evolved and has since become a vibrant area of active research, covering topics of superhydrophobicity/superhydrophilicity, superoleophobicity/superoleophilicity in gas or under liquid, superaerophobicity/superaerophilicity under liquid, and combinations of these states. The kinetic stu...

Bioinspired Interfaces with Superwettability: From Materials to Chemistry

Researches on the nanofluids have been increased very rapidly over the past decade. In spite of some inconsistency in the reported results and insufficient understanding of the mechanism of the heat transfer in nanofluids, it has been emerged as a promising heat transfer fluid. In the continuation of nanofluids research, the researchers have also tried to use hybrid nanofluid recently, which is engineered by suspending dissimilar nanoparticles either in mixture or composite form. The idea of using hybrid nanofluids is to further improvement of heat transfer and pressure drop characteristics by trade-off between advantages and disadvantages of individual suspension, attributed to good aspect ratio, better thermal network and synergistic effect of nanomaterials. This review summarizes recent researches on synthesis, thermophysical properties, heat transfer and pressure drop characteristics, possible applications and challenges of hybrid nanofluids. Review showed that proper hybridization may make the hybrid nanofluids very promising for heat transfer enhancement, however, lot of research works is still needed in the fields of preparation and stability, characterization and applications to overcome the challenges.

A review on hybrid nanofluids: Recent research, development and applications

When nanofluids are boiled, nanoparticles are deposited on the heater surface, causing a significant critical heat flux (CHF) enhancement. The authors examined the effect of the surface wettability and the capillarity of the nanoparticle deposition layer on CHF. It is well known that the deposition of nanoparticles changes the surface wettability, but it also causes capillary wicking on a porous surface, whereby the supplied liquid effectively delays the irreversible growth of a dry patch. This study demonstrates that the outstanding CHF enhancement in nanofluids is the consequence of both the improved surface wettability and the capillarity of the nanoparticle deposition layer.

Hyungdae Kim

Papers

Effect of nanoparticle deposition on capillary wicking that influences the critical heat flux in nanofluids

Effect of nanoparticles on CHF enhancement in pool boiling of nano-fluids

Experimental studies on CHF characteristics of nano-fluids at pool boiling

On the quenching of steel and zircaloy spheres in water-based nanofluids with alumina, silica and diamond nanoparticles

Pool boiling CHF enhancement by micro/nanoscale modification of zircaloy-4 surface